Biology 2 /SL Review Book Topic 6: Human Health & Physiology Name ______
Topic 6.3 Review Book: Defense against Infectious Disease
Key facts
1. A pathogen is an organism or virus that causes a disease.
2. Antibiotics are ineffective against viruses since viruses do not have their own metabolic pathways.
3. Antibiotics are effective against bacteria because they block the bacterium’s metabolic pathways.
4. Because human cells are different from bacterial cells, antibiotics do not harm human cells.
5. The skin and mucous membranes provide a barrier against pathogens.
6. Skin has sebaceous glands that secrete lactic acid and fatty acids. These secretions make the surface of the skin acidic, thereby controlling the growth of most pathogens.
7. Mucous membranes occur in the soft areas of the skin including the nose, trachea, vagina, and urethra. Mucous membranes produce an enzyme called lysozyme that kills many bacteria.
8. Some mucous membranes produce so much sticky mucus that they trap pathogens.
9. The blood contains white blood cells, some of which are called phagocytes. Phagocytes are able to identify pathogens and ingest them by phagocytosis.
10. Once the pathogens are inside the phagocytes, lysosomes release enzymes that kill and hydrolyze them.
11. Phagocytes are able to squeeze out of the capillaries to attack pathogens at the site of infection.
12. Antigens are foreign substances that do not belong in the body and thus stimulate the production of antibodies.
13. Antibodies are proteins that recognize and bind to antigens, thus destroying them.
14. Antibodies are quite specific. Since there are large numbers of different antigens, there are large numbers of different antibodies.
15. Antibodies are produced by a specific type of white blood cell called lymphocytes. Lymphocytes are quite specific so there is a different lymphocyte for every antibody produced.
16. Each type of lymphocyte puts some of its antibody on its plasma membrane. These lymphocytes have antigen-combining sites on their surface. When a pathogen enters the body, its antigens bind to the antibody specific for it which is on the surface of a circulating lymphocyte.
17. When the antigen binds to the antibody the lymphocyte is stimulated to produce copies of clones of it. These clones of cells produce large amounts of the specific antibody necessary to disable the incoming pathogen.
18. AIDS is known as a syndrome because it consists of a set of symptoms that are bound together. Ultimately AIDS decreases the ability of one’s immune system to function, thus weakening the body and eventually causing death.
19. HIV or human immunodeficiency virus is the pathogen that causes AIDS. This virus specifically attacks a lymphocyte known as a T-lymphocyte to cause the syndrome. Weakening and death is due to the death of the lymphocytes with the resulting inability to produce antibodies.
20. HIV can only survive very briefly outside the body and cannot easily pass through the skin.
21. Its transmission involves the transfer of body fluids from one infected person to an uninfected person. Means of transmission include skin breaks or cuts in the vagina, penis, mouth or intestine during vaginal, anal or oral sex.
22. HIV may also be transmitted via blood on hypodermic needles that are shared. It may also be transmitted via blood transfusions.
23. HIV may cross the placenta from mother to baby. It may also pass to the baby from mother during breast-feeding.
24. Social implications of AIDS include
A. Grief suffering by family and friends
B. Financial stress
C. Difficulty of AIDS patients in getting employment, housing, etc
D. Affecting sexual activity due to fear of the disease
25. Most feel there is a moral obligation of those with technology and financial resources to help those without such whom are suffering from AIDS. Africa, especially the southern region is highly affected by the disease.
ADDITIONAL NOTES
Please answer the following:
1. Define pathogen.
2. Why do antibiotics work against bacteria but not against viruses?
3. How do skin and mucous membranes defend us from pathogens?
4. What are phagocytic leucocytes?
5. Explain how phagocytic leucocytes ingest pathogens in the blood and in body tissues.
6. Distinguish between antigens and antibodies.
7. Outline how B lymphocytes produce antibodies in a typical immune response.
8. Define HIV and AIDS.
9. How does HIV damage the immune system?
10. Discuss the cause, transmission, and social implications of AIDS.